The northern river shark is one of two freshwater species discovered during a recent research effort completed in September 2008.

Previously, scientists had confused the shark with another species.

New marine animals will continue to turn up in future studies, scientists say.

''We're still describing new species from 10 or 13 feet [about 3 or 4 meters]" deep, said Clive Roberts, curator of fish at the Museum of New Zealand, "so it's no surprise that there are heaps of undescribed stuff further down."